Using x-ray arrays to measure impurity transport in the Alcator-C tokamak

Using three different x-ray arrays simultaneously, we have made measurements of the transport of aluminum (Z=13) or silicon (Z=14) injected into MIT’s Alcator tokamak plasma. Each array has ∼2 cm spatial and 15 μs temporal resolution. Since Alcator core temperatures are typically between 1 and 2 keV, fully stripped, H- and He-like ions are the only ionization states of the injected impurity with significant populations for r/a≲0.7. The spectral responses of the arrays have been tailored so that each array has a markedly different response to the x radiations from these three ionization states. Through the use of two of these arrays, time-resolved density profiles of fully stripped and total injected impurities, and studies of their transport, have been previously reported. Current work and description of the analysis method will be presented.